What does squawk 7700 mean?

How it works

A transponder answers radar with a four-digit code that the pilot sets, called a squawk. Each digit runs from 0 to 7 (the code is octal), so there are 4,096 codes, from 0000 to 7777. Air traffic control normally gives each flight its own code so that the radar can tell aircraft apart. A few codes have a fixed meaning instead, and these are what this table lists.

Three codes mean the same thing everywhere, and radar screens raise an alarm for them: 7700 is an emergency, 7600 a radio failure and 7500 unlawful interference such as a hijack. The rest depend on the rules of the place. Under the EU rules of the air (SERA.13005), a flight not receiving air traffic services sets 7000 and one without a code instruction sets 2000; Finland, Estonia, Denmark, France, Spain and the United Kingdom use these too, and Sweden uses 7000. In the United States a VFR flight sets 1200, and in Canada 1200 up to 12,500 ft and 1400 above it.

Example: a pilot flying VFR in Finland outside controlled airspace, not receiving air traffic services, sets 7000 as AIP Finland ENR 1.6 says. If the radio fails, the pilot sets 7600, and in an emergency 7700. Modern Mode S transponders also send the aircraft's own 24-bit address and its call sign, and ADS-B broadcasts the position and an emergency status with them.

Each row cites its source: the aeronautical information publication (AIP) of the state, the FAA Aeronautical Information Manual, the Transport Canada AIM or the EU regulation, as read on the checked date. Local codes, such as those for single aerodromes, are not listed, and an instruction from air traffic control always comes first.